excellent - maths is funny as well as clever, and I have a love of geeks, so maths is sexy too.

I love the 9 times tables trick with the fingers - that's a new one to me.

I like the "rules" about whether numbers are divisible by other numbers, eg:
if a number is divisible by 2, it will end in an even number (yeah, that's the obvious one);
if a number is divisble by 3, add up the digits that make the number, and if they are divisible by 3, so is the number (works for 6 if divisible by 6, and 9 if divisible by 9 and so on);
etc etc, I'm sure there's a list somewhere!